Study shows some have individualized personalities 31 July 2013, by Bob Yirka

scientists suspect that the more social an organism type is the more likely there are to be differing personalities within a group.

To learn which spiders might have which personality traits, the researchers went out into the field and bagged several nests and brought them back to the lab. After dissecting the nests, 40 specimens were chosen from each to serve as objects of study—each had colored spots applied to their backs to denote the level of aggression they exhibited when stimulated and to help in identifying them. Next, all of the spiders from the original nests were placed in artificial nests which were then placed in trees near the research facility. There, the lineatus. Credit: Wikipedia researchers simulated insects being captured in webs and studied the actions of the spiders that occurred as a result.

(Phys.org) —Researchers studying the In analyzing the data, the researchers found that spider in India have those spiders that had exhibited the most found that individual specimens have different aggression in the first part of the study, were the personality traits from one another. In their paper very same ones that acted most boldly when published in Proceedings of the Royal Society B, insects became stuck in their webs—suggesting that the team report that some spiders in the field study individualized personality traits in the spiders tends exhibited more "boldness" than did others. to determine which sort of job they have—those that are bolder tend to be the ones that deal with Scientists have known for many years that captured prey, while those that are meeker wind up have distinct personalities—cats and dogs are nurturing offspring or engaging in other less prime examples. Less clear is whether smaller confrontational tasks. organisms with smaller less developed brains do as well. To find out, the researchers in India More information: Individual personalities shape focused on Stegodyphus sarasinorum, one of the task differentiation in a social spider, Published 31 few spider species that live in colonies. Rather July 2013 doi: 10.1098/rspb.2013.1407 than focus on a range of different types of possible personalities, the team chose instead to focus on Abstract just one: boldness. With spiders, boldness is a Deciphering the mechanisms involved in shaping characteristic that describes a tendency to rush out social structure is key to a deeper understanding of of the nest to see what sort of creature has the evolutionary processes leading to sociality. become stuck in its web, rather than hanging Individual specialization within groups can increase behind watching to see what develops. colony efficiency and consequently productivity. Here, we test the hypothesis that within-group The researchers chose the spider colony because variation in individual personalities (i.e. boldness and aggression) can shape task differentiation. The

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social spider Stegodyphus sarasinorum (Eresidae) showed task differentiation (significant unequal participation) in simulated prey capture events across 10-day behavioural assays in the field, independent of developmental stage (level of maturation), eliminating age polyethism. Participation in prey capture was positively associated with level of boldness but not with aggression. Body size positively correlated with being the first spider to emerge from the colony as a response to prey capture but not with being the first to attack, and dispersal distance from experimental colonies correlated with attacking but not with emerging. This suggests that different behavioural responses to prey capture result from a complex set of individual characteristics. Boldness and aggression correlated positively, but neither was associated with body size, developmental stage or dispersal distance. Hence, we show that personalities shape task differentiation in a social spider independent of age and maturation. Our results suggest that personality measures obtained in solitary, standardized laboratory settings can be reliable predictors of behaviour in a social context in the field. Given the wealth of organisms that show consistent individual behavioural differences, personality could play a role in social organization in a diversity of animals.

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